ITV News' John Ray reports on the announcement that referendums are to be held across four Russian held regions in Ukraine.
Separatist leaders in four Moscow-controlled areas of Ukraine say they are planning to hold votes on whether to join Russia.
Referendums will be held in the Luhansk, Kherson and partly Russian-controlled Zaporizhzhia and Donetsk regions this week.
Ukrainian officials described the referendums - which are widely expected to go Russian President Vladimir Putin's way - as a "sham."
Meanwhile, the White House has labelled the developments as a "direct violation of Ukraine's sovereignty".
The announcement of the balloting, which is slated to begin on Friday, emerged after a close Putin ally said that they were needed.
During a trip to New York for the United Nations (UN) General Assembly, Ukraine's Foreign Minister, Dmytro Kuleba, described the referenda as an "act of desperation by Russia".
Speaking to ITV News Mr Kuleba added that Russia does "not deserve" a seat on the UN Security Council, though he accepted the possibility of revoking its membership is not straightforward.
"They [Russia] illegally took the seat in the UN Security Council as a permanent member and definitely they do not deserve to be there by any accounts. But it's doesn't work this way - we [can't] just kick them out," he said.
Ukraine Foreign Minister, Dmytro Kuleba, told ITV News' Robert Moore that Russia 'illegally' took a seat on the UN Security Council.
US national security adviser, Jake Sullivan, said Washington will "never recognise Russia's claims" if the referenda take place.
He said: "These referenda are an affront to the principles of sovereignty and territorial integrity that underpin the international system and that lie at the heart of the United Nations charter.
"We know that these referenda will be manipulated. We know that Russia will use these sham referenda as a basis to purportedly annex these territories, either now or in the future."
Announcing the ballots, former Russian President Dmitry Medvedev said folding Luhansk and Donetsk, in eastern Ukraine, into Russia itself would make the territories' redrawn frontiers “irreversible” and enable Moscow to use “any means” to defend them.
Annexing parts of Ukraine would amount 'unmistakably to a dismemberment of a major European nation' by Russia - Robert Moore reports.
The votes are unlikely to be recognised by other Western governments, who are backing Ukraine President Volodymyr Zelenskyy's counteroffensive with military and other support. The military aid has helped his forces seize momentum on battlefields in the east and south.
Speaking in New York, where he is also attending the extraordinary UN summit, German Chancellor Olaf Scholz said: “It is very, very clear that these sham referendums cannot be accepted.”
Latvian Foreign Minister Edgars Rinkevics called for more sanctions against Russia and more weapons for Ukraine, tweeting: “We must say no to Russian blackmail.”
In Donetsk, part of Ukraine's wider Donbas region which has been gripped by rebel fighting since 2014, separatist leader Denis Pushilin said the vote will “restore historic justice" to the territory's “long-suffering people."
He said the region's population “have earned the right to be part of the great country that they always considered their motherland".
Elsewhere, in partly Russian-occupied Zaporizhzhia, pro-Russia activist Vladimir Rogov said: “The faster we become part of Russia, the sooner peace will come.”
Pressure inside Russia for votes and from Moscow-backed leaders in Ukrainian regions which it controls increased after a Ukrainian counteroffensive - bolstered by Western supplied weaponry - recaptured large areas.
Russia's Kremlin controlled lower house of parliament has approved legislation which toughens the punishment for soldiers breaching their duties.
In an apparent effort to boost discipline within its ranks, the set of amendments to Russia’s Criminal Code was endorsed on Tuesday, in the State Duma.
The legislation introduces severe punishments for failure to follow orders, desertion or surrendering to the enemy.
It needs the upper house’s approval and then to be signed by Putin to become law.
Under the legislation, deserting the military during a period of mobilisation or martial law would be punishable by up to ten years in prison.
Harrowing pictures have emerged from a forest, outside the recaptured village of Izium over the past week, as Ukrainian officials claimed to have discovered torture victims in mass graves.
The governor of the Kharkiv region has claimed that the bodies of two children are among those recovered from hundreds of graves, in the wake of Ukraine's counteroffensive in the area.
Forensic experts who have exhumed the bodies of 146 people say many appear to be civilians, and that some bear the signs of a "violent death".
Yevhenii Yenin, a deputy minister in Ukraine’s Internal Affairs Ministry, told a national telecast the bodies revealed evidence of torture.
“These are broken ribs and broken heads, men with bound hands, broken jaws and severed genitalia,” he said.